The invention relates to improvements in methods of and in apparatus for making tobacco rods, for example, for making tobacco rods wherein a rod-like filler of natural, substitute and/or reconstituted tobacco is confined in a tubular wrapper of cigarette paper or other suitable wrapping material and which is ready to be subdivided into rod-shaped articles of the tobacco processing industry. More particularly, the invention relates to improvements in the treatment of tobacco particles on the way toward the stream and rod forming stations of a cigarette rod making or like machine. Still more particularly, the invention relates to improvements in methods of and in apparatus for treating tobacco ribs and foreign objects which happen to be admixed to more valuable combustible tobacco smoke generating constituents of rod-shaped smokers' products.
A modern cigarette rod making machine can produce one or more elongated rods which contain tobacco and are ready to be draped into cigarette paper or other suitable wrapping material prior to advancement through one or more cutters, one for each rod and each having means for subdividing the respective rod into sections of unit length or multiple unit length. The machine has at least one so-called distributor (sometimes called hopper) which converts a mixture of tobacco particles into a loose flow that is ready to be converted into a stream containing a surplus of tobacco particles. The surplus is removed by a so-called trimming or equalizing device, and the thus obtained trimmed stream or filler is condensed and draped into wrapping material to form a rod which is ready for subdivision into rod-shaped smokers' products. Conversion of the flow into a stream normally involves the utilization of an endless foraminous conveyor which cooperates with a suction chamber to attract successive increments at the leading end of the advancing flow and to form successive increments of a stream which contains the aforediscussed surplus.
Satisfactory treatment of tobacco particles in the distributor and during and subsequent to conversion of a loose flow of such particles into a stream is important because it greatly influences the quality of the ultimate products, e.g., plain cigarettes or filter cigarettes. For example, it is important to avoid excessive comminution of shredded tobacco leaf laminae because this could result in the generation of high percentages of short tobacco and tobacco dust. Furthermore, it is important to avoid excessive drying or moisturizing of tobacco particles. Still further, it is important to prevent relatively heavy, bulky and hard (sharp) fragments of tobacco ribs from puncturing the wrapping material for the tobacco filler. It is also important to ensure that the filler exhibit a desirable hardness as well as that particles of tobacco ribs be distributed in the filler in such a way that they are not likely to develop into relatively large glowing embers which are likely to fall out of the lighted end of a smokers' product to burn a hole in the floor and even set the surrounding area on fire.
Foreign particles, such as pieces of wire, nails, screws, bolts, nuts and/or plastic material, are also likely to find their way into the loose flow of tobacco particles and thence into the stream to thereby affect the quality of the cigarettes or other rod-shaped smokers' products.